Sydney: Black cockatoos, once numbering in tens of thousands and believed to "fly and call when rain is on the way", could become extinct within 50 years.

"They are iconic large forest cockatoos that were once widespread and common in huge numbers on the Swan Coastal Plain (in Australia)," said Ron Johnstone, adjunct professor at Murdoch University and ornithology curator at the Western Australia Museum.

He said there were three species, namely Carnaby`s cockatoo, Baudin`s cockatoo and the Forest Red-tailed Black cockatoo, that nested in tree hollows and moved south and west after nesting season to feed on nuts, nectar and wood-boring grubs and insects.

Johnstone said nuts from the extensive pine plantations introduced in the 1920s and 30s provided a valuable diet replacement for Carnaby`s cockatoos as developers gradually cleared Perth`s banksia heathlands for housing, according to a Murdoch statement.

"(When) a lot of the juveniles are just fledged...these areas became a very valuable source of food (which) the birds were able to use up very quickly because the pines are producing cones during the period when they first arrive," he said.

"That flock (of Carnaby`s black cockatoos) around the University of Western Australia grounds in Underwood Avenue is the last surviving flock in the western suburbs of Perth," he said.

"Now if you just continue to degrade and reduce the amount of available foraging habitat you will lose that flock."

Johnstone said developers and householders can choose to plant any of a variety of endemic and exotic trees that will help the black cockatoos survive.